The present invention generally relates to a material processing system and more particularly to micromachining with a laser.
It is known to employ femtosecond lasers for micromachining. The use of these ultrafast lasers has significantly improved the machining efficiency by quickly removing the workpiece material due to the instantaneous increase of the material temperature into a plasma regime. Furthermore, ionization of the material reduces splatter and debris during operation. An exemplary conventional device using a 50-200 femtosecond laser for micromachining is disclosed in U.S. Pat. No. 6,979,798 entitled “Laser System and Method for Material Processing with Ultra Fast Lasers” which issued to Gu et al. on Dec. 27, 2005, and is incorporated by reference herein. It is noteworthy, however, that a leading publication, P. Bado et al., Micromachining Handbook, Clark-MXR, Inc., version 2.3, chapter 14 (2001), discusses that there are “Shortcomings of Femtosecond Lasers” for conventional machining “because the rate of removal of material is dependent on average power, thruput is low. The technology that makes these ultrafast laser pulses does not produce high average power. Additionally, the technology is VERY expensive . . . . ”
Furthermore, conventional nanosecond laser induced breakdown spectroscopy suffers some limitations due to inefficient coupling of the laser pulse energy into a sample. The laser creates a plasma, which couples with the bulk (electron-phonon coupling) and supplies the energy for melting, followed by evaporation and excitation of the gas phase atoms. The inefficient coupling requires high energies per pulse, typically in the 10-100 mJ/pulse range, and leaves a scar caused by melting.
In accordance with the present invention, a laser material processing system and method are provided. A further aspect of the present invention employs a laser for micromachining. In another aspect of the present invention, the system uses a hollow waveguide. In yet another aspect of the present invention, a laser beam pulse is given broad bandwidth for workpiece modification. A further aspect of the present invention allows a single laser beam to simultaneously operate in multiple machining workstations and/or to machine multiple holes in the same workpiece. Additionally, a system includes a laser, pulse shaper and compensation device, and control system, with another aspect of the present invention. In a further aspect of the present invention, a system employs Multiphoton Intrapulse Interference Phase Scan to improve laser pulse performance. A method of operating a laser for micromachining is also provided.
The present invention is advantageous over conventional constructions since the equipment or the processing throughput used in the system of the present invention is significantly less expensive than traditional equipment. Furthermore, multiple workstations can be simultaneously powered by a single laser, thereby reducing the laser expense per workpiece. The novel waveguide of the present invention system also beneficially increases ps or fs pulse bandwidth so a less expensive, longer pulse lasers can be employed while improving micromachining efficiency. For another exemplary advantage, an inexpensive picosecond laser of the present invention, directly pumped by a flash lamp, is employed in some variations instead of considerably more expensive conventional femtosecond lasers, pumped by green laser sources; nevertheless, the present invention system provides the functional advantages of femtosecond ablation of the workpiece, in part, due to enhancing the laser pulse bandwidth instead of reducing the pulse duration. Multiphoton Intrapulse Interference Phase Scan and binary pulse shaping are further beneficial in accurately and inexpensively controlling ps or fs laser pulses for micromachining. The present invention advantageously uses laser induced breakdown spectroscopy with shaped pulses and/or MIIPS optimization, and with or without chirped pulses, for feedback and closed loop control of micromachining; the LIBS signal can provide an atomic signature of each workpiece layer when stacked so as to provide sensed feedback when each layer is completely penetrated whereby the controller automatically varies the process accordingly. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.